Automatic mooring winch



April 1942- w. SCHAELCHLIN 2,280,932

AUTOMATIC MOORING WINCH Filed Jan. 26, 1939 wiTNEssEs; INVENTOR ZZ/an h/lffnfchae/cb/lh. BY @ufiW fiiyue ATTORNEY Patented Apr. 28, 1942 AUTOMATIC MOORING WINCH Walter Schaelclilin, Wilkinsbnrg, Pa assignor to Westinghouse Electric & Manufacturing Collpany, East Pittsburgh. Pa a rporation of Pennsylvania Application January as, 1m, Serial No. 252,943

DCIaiml.

My invention relates to automatic mooring and towing winch control systems, and particularly to a control system for a mooring or towing winch employing a squirrel cage motor drive.

One object of my invention is to provide an automatic control system for a mooring or towing which, whereby the winch will be operated to pay out the mooring or towing cable as may be necessary, in order to maintain the cable tension at or below a predetermined magnitude and to heave in when the elective lengths of the cable exceed a predetermined magnitude.

When the winch is to be used on a ship, such as a tanker, carrying explosive materials, it is desirable that the motor for the winch shall be free of any operation that might generate a spark or an arc. A squirrel cage induction motor is therefore preferred for those applications, since it is free of collector rings or commutating devices on which arcs or sparks might develop during operation.

A further object of my invention, therefore, is to provide an automatic control system for a winch employing a squirrel cage motor.

In a system of this type in which a squirrel cage motor is employed, a problem is encountered when the cable tension exceeds the motor torque and tends to overhaul the motor. Under such conditions no energy is taken by the motor from the energizing circuit and the torque developed in the motor by its energizing current becomes zero. Under such conditions the motor tends to hold its equivalent synchronous speed constant up to extremely high torque values that may reach 600% of full load torque before permitting the speed of the motor to be increased to pay out cable in response to increased tension in the cable.

If the motor speed is kept constant inspite of the greatly increased torque and increased tension in the cable, an unnecessary and excessive stress is imposed upon the cable that may cause it to break. p

Another object of my invention, therefore, is to provide for the modification of the normal torque that would be developed in the squirrelcage motor under overhauling conditions, in order to enable the motor to increase its speed during such overhauling conditions to compensate more readily for the increased cable tension.

From the nature of the operation desired in a winch, the automatic control for the .winch should be such as to avoid hunting. For that reason, I prefer to employ a squirrel-cage motor provided with two sets of windings, one for high speed, and one for low speed operation. The usual automatic adjustments of the cable length by the winch to modify or change the cable tension when the tension is above a predeterthe low speed operation, will also be made available for use whenever the winch is to be operated manually, so that maximum flexibility of control may be achieved between the two speeds.

Among the other objects of my invention, therefore, are to provide a control system that will not hunt, and cause pumping or excessive reversal operation of the control system in the regulating action to maintain the cable tension at or below a predetermined magnitude; to permit simple adjustments of the tension in the cable in such manner as always to insure a proper balance between the motor torque and the tension; and, further, to provide a control system that shall be simple in its arrangement and effective in operation.

The manner in which the control equipment is applied to control the operation of a multispeed squirrel cage induction motor, in accordance with the principles of my invention, is illustrated in the accompanying drawing, in which,

Figure l is a simple diagram of connections of the mooring system according to my invention; ,and

Fig. 2 is a graph showing the torque speed curves of the motor under diflerent conditions.

As schematically shown in Figure 1, a mooring winch comprises an operating motor I which operates a drum or cable reel 2 through a suitable speed reduoer I, and a planetary torquemeasuring system 4, to control a mooring cable 6.

The low speed shaft 0 of the reducer I drives a sun gear or pinion l of the planetary system 4. Three planet gears I are disposed between the sun gear I and a ring gear 8. Each planet gear I is mounted upon a pin III of a spider l2 thatis rotatably supported on an extension 6' of shaft 0 from the speed reducer. Since the spider I2 is rotatably supported, and, in turn, supports the planet gears I, the torque reaction forces developed between the ring gear 9 and the planet gears 8 will be translated into a reaction force between the planet gears I and the spider I2. That reaction force will be propor-- tional to the torque ortension in the cable.

ment 8| engages contact the other contact fingers is disengaged.

To measure that reaction force upon the spider l2, and thus to measure the cable tension, a reaction arm I8 is connected to the spider I2 to oscillate with the spider l2 about the central axis of the planetary system 6.

The reaction arm I3 is disposed to press against an adjustable spring I4, which may be adjusted to provide a control reaction pressure to control the permitted tension range within which the cable tension may vary. The outer end of the torque arm It supports a segmental gear I5 to engage a pinion It on a shaft of an automatic control switch 26 of the drum controller type.- c

Energy for the motor I is derived from a suitable source (not shown) through conductors, 23 and certain pairs of contact members. of contactor switches numbered 2%, 2?, 28 and 36, respectively, which may be actuated to energize the motor according to the speed and the direction in which the motor is to function. The

motor I is provided with two sets of windings 33 and 35 in order to establish a low speed or a high speed of operation, according to which set of windings is energized. By way of illustration, the low speed windings 38 may be arranged to provide 32 poles, and the high speed windings 35, which are to operate the motor at high speed, may be arranged to provide 6 poles. It will read= The drum controller 2| is connected through the pinion I8 and the gear segment I5 to the reaction tension arm I8, on the winch, in such manner as to move the tension drum controller 2| to one terminal position or to the other, whenever the reaction arm I8 reaches a predetermined limit position in its movement in one direction or the other, according to the tension in the cable.

To control the automatic operation of the motor- I in the heave-.in direction of rotation, a reclaiming drum controller 69, responsive to the angular displacement of the drum 2 or to the length of cable 5 unwound from the drum, is provided. As illustrated in Fig. l, provision is made to reclaim or heave-in when the tension is at or below a predetermined magnitude only if the cable pay-out has exceeded a certain length. The reclaiming is done at high speed, but it will be understood that reclaiming may be done at slow speed, or provision may be made for reclaiming at high speed and transferring to slow speed just prior to the end oi the reclaiming cycle, it necessary, to avoid hunting. It will also be understood that the heave-in or reclaiming ily be understood that the two windings 33 and may be replaced by a winding that may be selectively connected for two speed operation of the motor 8.

Contact members 3's of the contactor switch '25 are provided to energize the motor in such a direction as to cause it to rotate the drum to heave in, and contact members 39 oi the switch 21 are provided to connect the motor to the circuit in such direction as to pay out the cable.

Contact members 65 of the switch 29 are connected to the high-speed windings 35. Contact members 43 of the switch M are connected to the low speed winding 33. Each conductor of the circuit between the contact members 39 and 48 contains a resistor 45. Cross-connecting conductors 4'I are provided between the conductors that connect the contact member 48 and the resistor 45, and the conductors that connect the contact members 81 and AI.

Contact members 49 of the contactor switch 5| are connected across a portion of each of the resistors 45. Means such as a current responsive relay 53 having contact members 56 and operating coil 51, ,is provided for controlling switch 5|, in a manner to be described hereinafter. Operating coil 51 is connected in the motor circuit so as to be energized only when the motor I is energized for operation in the pay-out direction of rotation.

In order to hold the motor I and drum 2 against rotation by the cable 8 when the system is not operating and the motor is deenergized, a brake 59 is provided.

To control the automatic operation of the motor I in the pay-out direction of rotation, the tension drum controller 2|, that is controlled by the reaction arm I3, is provided with four controller segments 6| to 64, inclusive, and with four sets of contact fingers to 68, inclusive. When operation of the motor I may be efiected as soon after any pay-out operation as the tension decreases below a predetermined magnitude.

Reclaiming controller 68 is provided with con tact segments 1I andr-I? and contact fingers 13 to 88, inclusive. Contact members 8i and 83 on fingers 65, but each of in switch 25 and contact members 85 on fast switch 29 are provided and electrically connected to reclaiming controllerfis as shown; only when it is desired to initiate the heave-in operation after the length of cable unwound from the drum has exceeded a predetermined length.

In order to permit manual control of the motor I, a drum controller 8'6 is employed. This controller is provided with interconnected contact segments 88 and 89, and with contact fingers 98 to 99 inclusive.

The contact fingers 96 to 99 inclusive, of the manual controller control the circuits through the automatic tension controller 2!, and reclaiming controller 68, to enable the manual controller 81 to assume complete control of the system.

When the manual controller 81 is in neutral or off, position, the segment 88 bridges the contact fingers to 99 inclusive.

When the cable tension increases above a predetermined magnitude, the reaction arm I3 will operate the tension controller 2| towards the left, and segments 62, Bland 64 will engage and energize contact fingers 66, 61 andGBrespectively.

Contact fingers 61 and segment 83 control the circuit to operating coil "II of "slow contactor 3|. That circuit extends from energized conductor I03, through contact fingers 95 and 98 and segment 88 of manual controller 81, contact fingers 61 and segment 63 of tension controller 2I, back interlock I85 of fast contactor 29, operating coil IIII 01 slow contactor switch-31; to energized conductor I01. When the control circuit is thus completed, contactor 3| is actuated to close the circuit through contact members 43 connected to the slow windings 33 of the motor I.

Contact fingers 68 and segment 64 control a circuit which may be traced from energized conductor I03 through contact fingers 95 and 99 and segment 88 of manual controller 81, contact fingers 68 and segment 64 of tension controller 2|, back interlock switch I88 01 "in contactor 25,

and operating coil III of out contactor 21, to energized conductor Hi1. Out contactor 21 will thereupon be actuated to connect the slow speed windings 33 of the motor I through the contact members 39, the closed contact members 49 of contactor switch 5i, 9. portion of the resistors 45, operating coil 51 of relay 53, and closed contact members 43 of the slow contactor 3i to the main circuit 23, to energize the slow speed windings 33 and to rotate the motor i slowly in a direction to pay out the cable to relieve the excessive tension developed therein.

At the same time, the brake 59 on the motor will be released or disengaged from the motor by the energization of the brake release coil through a circuit controlled by the contact fingers 3B, which may be traced from energized conductor Hi3 through segment 88 and contact fingers 95 and 96 of controller 8'1, contact fingers S6 and contact segment 62, and the operating coil of the brake 59, to bus conductor I01.

If the resistors 45 were not provided in the circuit to the motor I, the speed torque curve of the motor would be substantially as shown in the solid line curve A in Fig. 2. As shown on the right-hand side of the vertical ordinate base line, the speed drops off with an increase in torque in the forward driving direction, but the speed does not tend to increase very much in the negative torque direction which would correspond to the overhauling action by the cable. Because of such tendency of the motor to hold itself substantially at the speed corresponding to zero torque, an excessive tension would be do veloped in the cable because of the failure of the motor to rotate faster in response to the ver-= hauling tendency of the cable. Such excess tension in the cable would be relieved if the motor speed could be increased. Since the development of such excessive stresses in the cable may break the cable, it is desirable to modify the motor action to enable it to respond more freely to the overhauling tendency of the cable.

In order to control the motor torque during overhauling so that the motor will permit the cable to readjust its tension more rapidly, a portron of resistors 4.5 are utilized and they have the effect of modifying the torque of the motor so that the torque speed relationship will be substantially as indicated in the dotted line curve B in Fig. 2. As the cable tension increases'and tends to overhaul the motor, in order to readjust the cable tension within the predetermined range, the motor torque will be sufficiently di minished to permit the motor to be pulled out of its zero torque speed and to permit the motor speed to be increased. If the motor were designed to operate without the resistors 45, the speed value at zero torque at the point C might be made high enough, of course, to avoid the lock-in condition, but such speed would cause the motor to pay out too fast. and as a result the system would be subjected to excessive hunting action as the system would function to regulate the tension in the cable.

The motor will now operate in the pay-out direction of rotation. For normal operation, a portion of resistors 45 is shunted by contact members 49 of contactor switch 5!. In order to obtain additional control of the motor torque during overhauling caused by excessive tension, the current responsive relay 53 is provided. The operating coil 51 of relay 53 is energized by the current passing through resistor 45 to the motor I. If the operation is normal, that is, it the motor operates so that the rate of cable pay-out is sufficently great to relieve the excessive tension and the motor torque is such that the current through operating coil 51 remains below a predetermined magnitude, the relay 53 will not be actuated. However, when the motor speed is such that the excessive cable tension is not relieved, the motor torque, and therefore, the motor current, increases. When the current is above a predetermined magnitude, the relay 5'! is actuated to open contacts 55, thus deenergizing operating coil N3 of contactor switch 5|,

and thereby causing contact members 49 to open.

The resistance in. the motor circuit is thus increased causing the motor speed. to increase more rapidly as the motor torque increases. When the current decreases below the predetermined magnitude, the relay 53 is actuated to deenergize contactor 5i, and thus the motor i again operates as indicated by curve B.

The motor 5 will continue to operate in the Day-out direction until the tension of the cable diminishes to the predetermined magnitude of tension at which the automatic tension controller 2i was operated. "The tension controller 2! will thereupon be restored to its normal Off position and the contact segments 82, 63 and 64 will be disengaged from contact fingers 66, 67 and $8 to deenergize the various circuits and the operating coils connected thereto.

The circuit of the slow speed motor windings 33 will be opened by the opening of the contact members 3t and it of the out and slow contactors 2i? and ti, and the motor i and drum 2 will be held in position by the restored brake 5%, against displacement due to the tension of the mooring cable 5, if the effective length of cable or the total length of cable pay-out is below a predetermined magnitude. It the cable pay-out exceeds a predetermined length, the reclaiming controiler 39 will be effective to initiate the reclaiming operation of the motor 4.

The reciaiming controller 69 is actuated by the drum 2 and it may be so arranged that the contact fingers l3, "it and i! are bridged by segment ii and contact fingers "it and It are bridged by segment 32 when the drum starts to rotate in the pay-out direction of rotation. If the tension remains above the predetermined magnitude, cable pay o'ut will continue. When the cable pay-out has exceeded the gore-deter mined length, segment it also engages contact fingers iii and iii and segment iii also engages contact finger iiii. When the tension decreases to or below thepredeterrnined magnitude, the segment 88 oi tension controller 2i bridges contact fingers 65. Circuits are then completed to operating coils M5 and ill of iast" contactor 2t and in contactor 25, respectively, and to the coils of brake The circuit for operating coil H5 extends from energized conductor 5 33, contact fingers and 9'0, bridged by segment 38 of manual controller 81, contact ringers 35 bridged by segment iii of tension controller 7, contact fingers l3 and I6 bridged by segment H of reclaiming controller 89, operating coil H5, closed contacts H9, to energized conductor M1. The fast contactor switch 29 is thus actuated to close contact members 4i.

The circuit for operating coil H1 extends from energized segment H bridging fingers 13 and 15, operating coil H1, closed contacts Hi to energized conductor II". The in contactor 25 will thereupon be actuated to close contact members 4 31 to complete the circuit from the main supply source through conductors 29, contact members 91, contact members 4| to the high speed winding 35 of the motor I.

The circuit for energizing the coil of brake 59 drum 2 to heave-in the cable 5. As the heavein or reclaiming operation continues, the reclaiming controller 89 is actuated in the direction to disengage segment 1| from contact fingers 15 and 18, and segment 12 from contact finger 88. However, the circuit for energizi the opthe left, contact fingers 99, 94 and 95 will remain energized to keep the in" contactor 25 closed and the brake 59 released. Contact finger 92 will bedeenergized to open slow" contactor 3| and contact finger 9| will be energized to close fast" contactor 29. The in and fast" contact members 91 and 4| will connect the high speed windings 95 of the motor I' to the supply circuit 23, to operate the motor at high speed to heave in the-cable.

When the motor is to be operated to pay out Y cable, the manual drum controller 81 will be moved towards theright. When the controller erating coil H5 is maintained through the holding circuit established through the cqntact members 85. Similarly, the circuits for energizing operating coil H1 and coil of brake 59 are maintalned through contact members 8| and 83, respectively. The heave-in operation continues until segment N disengages from contact fingers 13, 14 and 11, and segment 12 disengages from contact fingers 18 and 19, thus deenergizing operating coils II5 and H1 and the coil of brake 59. The circuit of the high speed motor winding 35 will be opened by the opening of contact members 31 and III of the in" and "fast" contactors and 29, respectively, and the drum 2 will be held in position by the restored brake 59, against displacement due to the tension of the cable 5.

Should the cable tension increase above the predetermined magnitude during the heave-in operation, the tension controller 2| will be actuated to open the circuit through contact fingers 85 and segment 8| to deenergize the operating coils H5 and I" to terminate the heave-in operation, as hereinabove described, and to establish circuitfor eflecting operation in the pay-out direction of rotation.

moved from its neutral position, segment 88 is disengaged from contact fingers 98, 91, 98 and 99 to open the various control circuits from the automatic tension controller 2| and reclaiming controller 89. The manual controller 91 will then assume control according to the direction in which it is moved, and according to the position to which it is moved in either of such directions.

when the motor Us to be operated to reel in cable, the manual controller 81 should be moved to the left. When the controller 81 is moved to the left, contact fingers 90, 92, 94 and 95 will be bridged by segments 89 and 88 at the first position to energize the operating coils H1 and II of in" and slow" contactor switches 25 and 3|, respectively, and the brake release coil 59. The slow speed windings 39 of the motor I will be connected to the main circuit by contact members 91 and 49 through cross-conductors 41, and the brake 59 will be released from the motor I.

If the controller 81 iS then shifted further to 91 is moved to the right, at the first position, contact fingers 92, 99, 99 and 95 will be energized to close out and slow" contactor switches 21 and 3| to energize the. slow speed windings 39, and to release the brake 59. The motor I will be operated in the reverse direction from the previous operation by reason of the reversed phase connections relative to the cross connect-- hold contactor 21 closed and to hold the brake 59 open. Contact finger 92 will be deenergized to open the slow" contactor 3|, and contact finger 9I will be energized to energize the operating coil II5 of fast" contactor 29.. The high speed motor windings 35 will now be energized from the main circuit through the out" contact members 39, contact member 49, a portion of the resistors 45, the cross-connecting conductors 41 and the fast" contact members ll.

When the desired condition of the cable is attained, the manual controller handle I23 may be released, and it will resume its normal intermediate oiP position in response to the balanced forces of the restoring springs I25 and I21. The automatic control function will thereupon be restored to the automatic tension controller 2I and reclaiming controller 89 by the reclosure of the neutral segments 99, 91, 98 and 99 of the manual controller 81.

By the provision of two windings or a two speed winding in the motor I, for slow and for fast operation, and the associated control equipment operating as described, a squirrel-cage motor may be utilized for winch service and safely employed in applications where sparks or are might be generated by a commutator or slip ring to present a dangerous hazard.

, My invention, therefore, contemplates the use of a squirrel cage motor provided with a multispeed winding combination to control the operation of a winch, with the addition of torque modifying means to prevent the motor from establishing a lock-in condition that would prevent the motor from rotating above such lock-in speed when the cable tension became excessive and tended to overhaul the motor.

My invention is not limited to separate windings in the motor, since the same windings may be .arranged to establish different numbers of poles for high speed and low speed conditions.

Similarly,- the tension measuring and control equipment may be modified without departing from the spirit and scope of the invention as set forth in the appended claims.

I claim as my invention:

l. A winch system comprising a squirrel cage motor provided with one set of stator windings for slow speed operation and a second set of stator windings for high speed operation, a source of energy for the motor, a reeling drum operated by the motor, a cable operated by the drum, means responsive to the cable tension, said means including a controller movable to a high tension position in response to cable tension in excess of a predetermined value and movable to a low tension position in response to cable tension less than a predetermined value, a controller operable in response to the length or cable paid-out by said reeling drum, switching means controlled by the second mentioned controller when said cable tension responsive means is at its low tension position to connect .the high speed windings of the motor to the source to operate the motor in a direction to heave in the cable, and further switching means controlled by the controller when said cable tension responsive means is at its'high tension position to connect the slow speed windings of the motor to the source to operate by the motor in a direction to pay out the cable to diminish the cable tension.

2. A winch system comprising a squirrel cage motor provided with one set of stator windings for slow speed operation and a second set of stator windings for fast operation, a source of energy for the motor, a reeling drum operated by the motor, a cable operated by the drum, means responsive to the cable tension including controller means, said controller means being movable to a high cable tension position in response to cable tension in excess of a predetermined value and movable to a low cable tension position in response to cable tension less than a predetermined value, and means operated by said controller means, when the latter is moved to high tension position, to connect the motor windings to establish slow speed pay out rotation, and further controller means operable by said drum being effective, when the tension-=responsive controller means is moved to low tension position, to connect the motor windings to establish high speed heave in operation.

3. In a winch system, the combination with a multi-speed squirrel cage induction motor, a reeling drum operated by the motor, a source of energy for the motor, a cable operated by the drum, means for selectively connecting the motor to the source to reel in or to pay out at predetermined speeds, resistance means connected to the motor circuit to modifythe torque characteristic of the motor, under cable overhauling conditions, to prevent a substantial lock-in of the motor at synchronous speed, and means responsive to the motor current for controlling the said resistance means.

4. A winch system comprising a squirrel cage induction motor provided with a multi-speed winding, a source of energy for the motor, a reeling drum operated by the motor, a cable operated by the drum, tension control means responsive to the cable tension for connecting the motor to the said source for slow speed operation in the pay-out direction of rotation when the cable tension is above a predetermined magnitude, and reclaiming control means responsive to the efiective length of the cable and electrically connected to the tension control means for connecterated by the drum, tension control means responsive to the cable tension for connecting the motor to the said source for operation at a pre determined speed in the pay-out direction of rotation when the cable tension is above a predetermined magnitude, and reclaiming control means responsive to the effective length of the cable and electrically connected to the tension control means for connecting the motor to the ing the motor to the said source for high speed operation in the heave-in direction of rotation when the cable tension is at or below a predetermined magnitude.

5. A winch system comprising a squirrel-cage induction motor provided with a multi-speed winding, 2. source of energy for the motor, a reeling drum operated by the motor, a cable opsaid source for operation at a predetermined speed in the heave-in direction of rotation when the cable tension is at or below a predetermined magnitude.

6. A winch system comprising a squirrel-cage induction motor provided with a multi-speed winding, a source of energy for the motor, a reeling drum operated by the motor, a cable operated by the drum, tension control means responsive to the cable tension for connecting the motor to the said source for operation at a predetermined speed in the pay-out direction of rotation when the cable tension is above a predetermined magnitude, control-means responsive to the motor current for adjusting the speed torque characteristic of the motor in the payout direction of rotation in response to a predetermined change in the motor current, and reclaiming control means responsive to the effecti-ve length of the cable and electrically connected to the tension control means for connecting the motor to the said source for operation at a predetermined speed in the heave-in direction of rotation when the cable tension is at or below a predetermined magnitude.

7. A winch system comprising a squirrel-cage motor provided with one set of stator windings for operation at a first speed in one direction and a second set oi stator windings for operation at a second speed in another direction, a source of energy for the motor, a reeling drum operated by the-motor, a cable operated by the drum, braking means effective to prevent rotation of the drum when said motor is disconnected from. said source, means responsive to the cable tension, means responsive to the effective length of the cable, switching means controlled by said means responsive to cable tension for connecting said stator winding to said source for operation at said first speed when the cable tension is above a predetermined magnitude, and switching means controlled by said means responsive to the cable length for connecting said stator winding to said source for operation at said second speed when the effective length exceeds a predetermined magnitude, said first switching means, responsive to cable tension when the tension is below a predetermined magnitude adapted to control the operation or the second named switching means.

8. A winch system comprising a squirrel cage motor provided with one set of stator windings for slow speed operation and a second set of stator windings for high speedoperation, a source oi alternating current energy for the motor, a reeling drum operated by the motor, a cable operated by the drum, means responsive to the cable tension, 9. controller operated by the said means responsive to cable tension, said controller being movable to a high tension position when the cable is subjected to a given high tension and being movable to a low tension position when the cable is subjected to a given low tensions, means responsive to the cable length paidout by said reeling drum, a second controller operated by the means responsive to the cable to the tension in the cable or at high speed in response to the length of the cable paid-out by the reeling drum.

9. A winch system comprising a squirrel cage motor provided with one set of stator windings for slow sped operation and a second set of stator windings for high speed operation,a source of alternating current energy for the motor, a reeling drum connected to be operated by the motor, a cable wound on the drum to be thus either paid-out or heaved-in by the drum depending on the operation of the drum, means responsive to the cable tension, a controller operated by the means responsive to the cable tension, said controller being movable to a high tension position when the cable is subjected to a given high tension and being movable to a low tension position when the cableis subjected to a given low tension, means responsive to the cable length paid-out by said reeling drum, a second controller operated by the means responsive to the cable length paid-out by the reeling drum, first switching means for connecting the slow speed windings of the motor to the said source of alternating current to operate the reel-. ing drum to permit paying out cable, and second switching means for connecting the high speed windings of the motor to the said source of alternating current to operate the reeling drum to heave-in cablewhen the cable length paidout is above a certain length, said controllers being interconnected to control said two switching means to pay-out cable at a slow speed or to heave-in cable at a high speed when the tension is at the low value and paid-out cable length is above a certain value.

- WALTER SCI-IAELCHIJN. 

